These cutting devices have been known for some time. They are mainly employed for cutting printed paper webs such as those that are required by larger companies in the finance or insurance industry. These are high performance paper processing lines that typically include high speed printers, power cutting devices as well as sorting and optionally enveloping devices and that are directed to a mostly automated operation.
In order to ensure the safe operation at such high turnovers and speeds a number of precautions need to be taken. For example, the calm and safe guidance of the paper web is of central importance. Another problem is the introduction of the paper into the cutting device. In order to conduct a safe lateral paper separation with sufficient quality for all purposes that should not show any traces of paper rupture the paper web must be halted for a short moment prior to and during its lateral separation. Consequently, it follows that the paper web is moved at different speeds at the location of the lateral separation device or experiences different phases of movement. Next to a phase of constant speed that may be short or even absent during practical operation, phases of acceleration as well as a phase of braking to a complete stop are also required. This results in an average speed that corresponds to the speed of paper introduction and equals the operation speed of a continuously working device.
Because these high performance paper processing lines should operate mostly continuously and without interruption, measures must be taken to accumulate the paper web in a certain region of the processing line or the cutting device (braking or stopping phase) in order to reduce the accumulated material subsequent to the effected lateral separation during an acceleration phase and to continue with normal motion (constant speed). When doing this one has to ensure that the acceleration phase does not last too long because ruptures of the paper web could occur.
From DE 100 11 006 a device for cutting paper webs with a pneumatic paper retarding device is known, where the paper web is guided by means of an air stream acting from below the web through a loop directed upwards.
The web retardation of a device for cutting paper webs described in EP 1 268 329 and WO 01/66448 relies on the above principle.
It is unsatisfactory for these known devices that the accumulated paper web is unguided for a moment and because of this it can make uncontrolled movements upon subsequent acceleration. A further disadvantage is that in this manner only one paper web can be retarded at a time.
It is therefore a first object of the invention to offer a device, wherein the paper web is guided loosely despite its accumulation, i.e. without too much tension, actually being in contact with a mechanical guide means at all times. According to the invention this object is solved while at the same time avoiding the disadvantages of the state of the art by a first embodiment of the invention.
The invention also relates to a method for the lateral separation of fast moving paper webs.
Applicant's investigations leading to the present invention have demonstrated that it is actually possible to increase the turnover of such a processing line even further by employing wider paper webs that are separated longitudinally prior to being introduced to the lateral separating device. For this purpose the paper web is initially introduced to a longitudinal separating device, i.e. before entering the buffer region of the device, which cuts the paper web in machine direction and produces two paper webs arranged on top of each other of half the width of the paper web. By mechanical measures it is ensured that that both partial webs run synchronically so that their further processing can be done simultaneously. Subsequently, both partial webs are guided to the buffer region. There the webs are slowed down independently of one another and accumulated and again accelerated.
In order to optimally benefit from such a longitudinal separating device it is necessary to introduce both formed partial webs simultaneously into the cutting device or its own cutting devices. When doing this the problem must be solved that the device for accumulating the paper web in the buffer region of the processing line cannot serve both partial webs at the same time und would therefore have to be provided twice, thus leading to a significant additional effort for its design, this not having been cost-effective for devices of the state of the art. Furthermore, the requirement of synchronized movement of the partial webs poses an unsolved problem.
Hence, it is a second object of the invention to provide a relatively simple design for the device in the buffer region of the processing line that can process both partial webs at the same time while minimizing the risks of loosing synchronicity, i.e. the synchronous movement of the webs, this being achieved with the embodiments.
Skilled people in the art designate the number of partial webs as group size. If the paper web is separated longitudinally once, the group size is 2. However, it is another object of the invention to provide a design for the buffer region that can also process group sizes larger than 2 or even odd groups. With odd group sizes it can be the case that only one paper web is moved forward. In this case the difference in length of the lower and upper paper web is compensated by the buffer.
In general the present invention offers a device and a method for the lateral separation of paper webs, comprising a paper introduction region, which optionally may include a longitudinal separation device for longitudinally separating the paper web into two partial webs, a buffer region, where at least one web is prepared for the discontinuous forward motion, a controller, a cutting device and a paper lead-off region. The paper introduction region optionally includes a longitudinal separation device with a cutting means that is arranged at the desired location of separation, typically in the middle of the device, the exact position of the cutting means being finely adjustable. The region for the paper introduction comprises the driven web supply roller(s) for supplying the paper web or the partial paper webs. The paper introduction region is positioned at that location of the processing line where—depending on the specific embodiment—the original paper web is introduced or at the exit of the device for the longitudinal separation of the paper web, where both partial webs are introduced for further processing.
The buffer region that is arranged between the paper introduction region and the paper lead-off region comprises one tube group with two tubes that are movable relative to at least one third tube perpendicular to the web. The tubes of this group are more like tubes or tubular surfaces on which the paper web glides. This tube group is arranged between the continuously or discontinuously driven web supply roller and the discontinuously driven web feed in order to form a double turning web loop of variable length. The length of this web loop, that is determined by the distance between the tubes of the tube group, is controlled by a controller. By moving the movable tubes away from the stationary tubes the device adapts to the double format length of the lateral separating device. Because no driven tubes participate in this action and instead the paper webs are dragged over smooth tube surfaces no undesired or erroneous pulling or dragging of the web occurs that would involve the danger of rupture. In contrast to the devices of the state of the art no air is blown into the web loop for it not to collapse but instead the loop is guided by means of at least three non-driven tubes making up a tube group, where the guidance is dictated by the additional paper material present. The control of the aims with the movable tube is the task of the controller.
A paper web being termed as “fast moving” in accordance with the invention is one working satisfactorily at a speed of at least about 120 meters per minute (m/min), preferably at least about 160 m/min and, in particular, in the range of about 180 to 210 m/min. The term “about” used in this context is meant to designate a deviation range of ±20%.
A speed in the latter mentioned range allows for a cutting frequency of about 40000 cuts per hour during operation, the use of two webs bringing this to twice the number of documents.
If the processing line has an upstream longitudinal separation device, the above mentioned device must be present twice in the buffer region, one for each partial web. According to the invention this is solved by arranging a laterally reversed but otherwise identical tube group, which also comprises at least three stationary tubes, adjacent to the first group, so that the carrier means to which these tube groups are attached are arranged symmetrically to the plane and each encompasses an angle of about 75° together with the paper web.
The controller is connected to the continuously or discontinuously driven web supply roller and the discontinuous web forward motion and calculates the necessary spreading of the movable tubes from the difference in forward motion. Furthermore, the controller determines the continuous web forward speed (for the continuous forward motion) and initiates the discontinuous web forward motion that is coordinated with the cutting operation.
The paper web stops for the cutting operation. At this point in time the paper webs moved by the continuous or discontinuous web supply have accumulated and the movable tube pairs of the tube groups move away from the stationary tubes to take up the accumulated material. Their guides are tilted a little from the line vertical to the paper moving direction towards the cutting device. When each of the tube groups has picked up paper of a predetermined length l from a side to be cut, the cutting step is effected and the discontinuous web feed motion starts again and accelerates the webs to a higher speed than the continuous or discontinuous web feed in minimal time. At the same time the tube groups move together again and release the accumulated material. The acceleration of this synchronized web forward motion is calculated so that it reaches the continuous or discontinuous web speed or switches to the braking phase at that point, when the complete accumulated reserve is stretched. Then, a further braking is initiated to take up the web length l before a next cut is initiated, where both partial webs are separated simultaneously.
The continuous or discontinuous web supply is accomplished by two adjacently positioned driven rollers that are located before to the buffer region. The discontinuous paper forward motion is accomplished by the driven rollers in the web lead-off region following the buffer region.
A piece of paper passing the lead-off device after lateral separation is not processed further and will now, for example, be placed alone or with other separated paper pieces in an envelope or is collected together with further separated paper pieces in a stack for packaging purposes. However, these further steps are well known to the skilled person in this field and do not require any further explanation. Also, they are not part of this invention.
A general advantage of the present invention is the possibility to process paper webs continuously with high throughput. A further advantage is that the synchronized forward motion mechanism does not affect the whole web but only the accumulated parts of the paper webs. This means that smaller masses need to be accelerated and decelerated, thus making the use of engines with lots of power and large torque obsolete even though the discontinuous forward motion requires considerable accelerations. On the other side, there are no special requirements for the continuous or discontinuous web supply drive. The packaging machine that fetches the documents in groups determines the cycle time. This mode of operation allows for stopping the cutter after each separation.
An important advantage of the device according to the invention is that the paper webs are guided at any point in time, i.e. they always have contact to some rollers or tubes, whether driven or not, over the whole length of the accumulated material. This leads to a better engine smoothness and ensures that the webs do not have an undesired opportunity to be crinkled or ruptured.